Sintered iron based articles infiltrated with copper based metals

ABSTRACT

A SINTERED METAL ARTICLE INCLUDING A SINTERED SKELECTION HAVING THE COMPOSITION 1.5-2.0% NICKEL, 0.3-0.7% MOLYBEDNUM, 1-2% COPPER, 0.1-.3% CARBON, NOT MORE THAN 2% OF MANGANESE, SILICON, SULPHUR, AND PHOSPHORUS TOGETHER (PERCENTAGES BEING BY WEIGHT), THE REMAINDER (APART FROM IMPURITIES AND TRACE ELEMENTS) BEING IRON, THE SINTERED SKELETON BEING INFILTRATED WITH COPPER OR COPPER-BASE ALLOY, AND THE ARTICLE BEING CASE-HARDENED.

3,829,295 SINTERED IRON BASED ARTICLES INFILTRATED WITH COPPER BASED METALS Edwin Bruce Farmer and Terence Michael Cadle, Coventry, England, assignors to Brico Engineering Limited, Coventry, England No Drawing. Filed Oct. 13, 1972, Ser. No. 297,363 Claims priority, application Great Britain, Oct. 23, 1971, 49,345/71 Int. Cl. B22f 3/26 US. Cl. 29-1821 6 Claims ABSTRACT OF THE DISCLOSURE A sintered metal article including a sintered skeleton having the composition 1.5-2.0% Nickel, 0.30.7% Molybdenum, 1-2% Copper, 0.1-0.3% Carbon, not more than 2% of Manganese, Silicon, Sulphur, and Phosphorus together (percentages being by weight), the remainder (apart from impurities and trace elements) being Iron, the sintered skeleton being infiltrated with Copper or Copper-based alloy, and the article being case-hardened.

This invention relates to sintered metal articles and to processes for their manufacture.

According to this invention in one aspect, a sintered metal article includes a sintered skeleton having the composition 1.5-2.0% Nickel, 0.3-0.7% Molybdenum, 1-2% Copper, 0.10.3% Carbon, not more than 2% of Manganese, Silicon, Sulphur and Phosphorus together (percentages being by weight), the remainder (apart from impurities and trace elements) being Iron, the sintered skeleton being infiltrated with Copper, or Copper-based alloy, and the article being case hardened.

Preferably the skeleton has substantially 1.75% Nickel, 0.5% Molybdenum. 1.5% Copper, 0.25% Combined Carbon.

According to this invention in another aspect, a process for the manufacture of sintered metal articles includes the steps of producing a sintered skeleton having the composition l.5-2.0% Nickel, 0.30.7% Molybdenum, 12% Copper, 0.l0.3% Carbon, not more than 2% of Manganese, Silicon, Sulphur and Phosphorus together, the remainder (apart from impurities and trace elements) being Iron, infiltrating the skeleton with Copper or Copper-based alloy in an amount between 8% and 25% of the skeleton, and then case-hardening the infiltrated article.

Preferably the sintered skeleton is infiltrated with 14% Copper or Copper-based alloy.

A process for the manufacture of articles in accordance with the invention will now be described by way of example.

A pre-alloy or partial pre-alloy in the form of a powder of less than 100 13.8. mesh size and the following composition is selected:

Percent Ni 1.5-2 Mo 0.3-0.7 Cu 1.0-2.0 Mn, Si, S, P Fe Remainder 1 Not exceeding 2% in total. (all the percentages in the specification are by weight).

This pre-alloy or partial pre-alloy powder is mixed with 01-03% (of the weight of the pre-alloy powder) of Carbon, in the form of graphite, and preferably with a small percentage e.g. 1% of a suitable lubricant such as Zinc Stearate. The constituents are thoroughly mixed in a suitable mixer.

3,829,295 Patented Aug. 13, 1974 The mixture is then pressed at 30-45 tons/sq. in. in a suitable powder metallurgy press, and sintered in a protective atmosphere, for example, a reducing atmosphere of dried cracked Ammonia or a Carbonaceous atmosphere of Endothermic Gas at a temperature in the range 1090 C.-ll20 C. for between 20 and 30 minutes. The lubricant disappears in the sintering process.

The sintered article or skeleton is then infiltrated with Copper or Copper-based alloy in an amount equal to between 8 and 25 of the weight of the article, for example, by placing the article in a suitable mould having walls which extend above the article and placing Copper or Copper-based alloy powder on the article, between the walls. The article is then heated in an oven to a temperature significantly above the melting point of Copper or its alloy, so that all the molten Copper or Copper-based alloy infiltrates into the pores of the article; the time of heating is such as to allow the Copper or Copper-based alloy to infiltrate the article uniformly.

Suitable Copper-based alloys are Copper plus 3% Cobalt, or Copper plus 5% Iron and 5% Manganese.

After infiltration the article is then case-hardened either by Carburising, Carbo-Nitriding or any other known or convenient method of Carbon case-hardening.

In one particular example the pre-alloy powder contained 1.75% Nickel, 0.5% Molybdenum, 1.5% Copper, which was mixed with 0.25% Graphite and 1% Zinc Stearate. After sintering in the above manner the skeleton was impregnated with 14% Copper.

The ultimate tensile strength of the article is shown by the following table:

Condition UTS, tons/sq. in. As sintered 27 Sintered and case-hardened 46 Sintered, infiltrated and case-hardened 65 Condition UTS, tons/sq. in. As sintered 27 Sintered and case-hardened 41 Infiltrated and case hardened 40 Other physical properties of articles made in accordance with the invention have been measured as follows:

Density gm./cc 7.0-8.0 Transverse rupture modulus p.s.i. 270,000 Impact strength (unnotched Charpy) ft. lb 27 We claim:

1. A sintered metal article consisting of a sintered skeleton infiltrated with copper or copper-based alloy, the skeleton having the composition, in percentages by weight:

Percent Nickel l.5-2.0

Molybdenum 0.3-0.7

Copper 1-2 Carbon 0. l0.3 Manganese, Silicon, Sulphur and phosphorus together Not exceeding 2 Iron (with impurities and trace elements) 93.0-97.1

3 4 the skeleton being infiltrated with Copper or Copper-based References Cited alloy, and the article being case-hardened after infiltration. UNITED STATES PATENTS 2. A sintered metal article, according to Claim 1, in whi h th skeleton has substantially 1.75% Nickel, 0.5% 3414391 12/1968 Brab 29' 182'1 Mo1ybdenum,1 5% COpper0 25% Carbon 3,694,173 9/1972 Farmer et al. 29182.1

3. A sintered metal article, according to Claim 1, in FOREIGN PATENTS which the infiltrated Copper or Copper-based alloy 1,071,3 3 19 7 Great i i 29 1 2 1 amounts to 8-25% of the skeleton. 720,050 12/1954 Great Britain 29-182.1

4. A sintered metal article, according to Claim 3, infiltrated with 14% Copper or Copper-based alloy. 10 C L D- Q ARFORTH, Primary Examiner 5. A sintered metal article, according to Claim 1, which 13 HUNT Assistant Examiner is case-hardened by carburising.

6. A sintered metal article, according to Claim 1, which US. Cl. X.R. is case-hardened by carbo-nitriding. 15 29--182.5, 182.7 

